Generation of low-EMI PWM patterns for induction motor drives with chaotic maps

Electromagnetic radiation of power switches is an intrinsic characteristics of modern power conversion, since electronic converters adopt switching techniques, where the transistors are operated at very high frequencies, from a few kHz to some MHz. The availability of reliable, fast and efficient power switches has spread the adoption of power inverters in many industrial applications. Among them drives for pump, high performance fan, heating systems, traction, are the most common areas of application. Recently, increasing attention has been focused on the emission of electromagnetic radiation of the converters which are commonly operated at fixed frequency at several amps, depending on the size of the motor. This results in a peak in the current spectrum at the switching frequency, which affects directly the emission of radiations and indirectly acoustic noise and mechanical vibrations. In this paper the design of chaos-based PWM (CB-PWM) for DC/AC converters for electric drives is investigated. The drive prototype will allow the experimental validation of EMI produced in a shielded or anechoic room, and the evaluation of drive performances, from the point of view of torque ripple and efficiency. From theoretical analysis and experiments it is shown that a reduction of the peak emission around the switching frequency up to 20 dB, without affecting performances.